An inherent problem of the single-lens reflex digital camera, due to its structure, is that, unlike the lens-integrated type in which the lens cannot be changed, an image sensing unit composed of an image sensor and the like is exposed to the outside air. As a result, dust adheres to the low-pass filter and the like on the image sensor such as a CCD or a CMOS, resulting in the sensing of images in which the dust is evident.
In order to solve this sort of “dust problem”, hardware countermeasures that physically reduce dust and prevent the appearance of dust are of course important. However, at present, support using a software application (a PC application) is required for the retouching of an image in which dust appears when the image is sensed with a camera for which such hardware countermeasures are not taken.
There are two possible methods of solving the problem of dust by retouching the image using a PC application: Automatic dust reduction using image analysis, and area reproduction. The former method reduces dust by identifying the location of dust from the image and replacing the pixels of dust with pixels obtained by predicting what should have been sensed if dust had not existed. The latter method eliminates dust by blending pixel values from other areas into the areas in which dust appears (dust areas). With the latter method, a user of the PC application can manually remove dust by specifying a copy source area (an area of the same or similar color tone as the dust areas) and a copy destination area (the dust areas).
The automatic dust reduction method is a PC application-based automatic process and thus the user's operation is easy. However, the image analysis process is complicated and requires an image for the purpose of detecting the dust areas and the like, and moreover, there is a risk of picture quality deterioration and the like due to mistaken identification. On the other hand, the area reproduction process requires the user of the PC application to specify the areas manually, and therefore, more user's operations than those required in the automatic dust reduction method are required, however, the output results match the intentions of the application user.
The area reproduction process is a commonly equipped function of an image modification PC application typified by Adobe PhotoShop®. The area reproduction process is described, for example, as the “copy stamp” function described under the entry “copy stamp” in the “digital word dictionary” [online search Dec. 1, 2004] at the following internet address: <URL:http://www.nifty.com/webapp/digitalword/word/080/08091.htm>.
However, an ordinary image editing PC application can save an image obtained by editing the original image (edited image) either by replacing (discarding) the original image or as a new file while the original image data being intact. Therefore, once the edited image is saved, if the user then wishes to undo or change the edit operations applied to the image, the user has no choice but to either redo the editing from the beginning using the original image or close one's eyes to a certain deterioration in the quality of the image and apply a further modify to the modified image. In addition, where a plurality of substantially identical cuts are present, as with commercial image sensing and the like, it is necessary to specify the contents of the modification process for each cut to which it is to be applied, which is time-consuming and inconvenient.